1. Field of the Invention
This invention relates to the manufacture of composite containers and primarily to the manufacture of a hollow tubular plastic sleeve or label which is subsequently heat-shrunk onto the body portion of a hollow glass or plastic container. The sleeve is preferably formed from a continuous web or roll of heat-shrinkable oriented thermoplastic material immediately prior to its application to the container. Alternately, the sleeve may be preformed, flattened and stored, and later taken to a position adjacent the container where it is opened and moved into telescopic alignment with the container retained in upright relation. The final shrinking of the sleeve into tightly engaging condition around the container body is normally preformed by subjecting the sleeve to controlled hot air or infrared radiation heating during passage of the aligned surrounding sleeve and container through a tunnel oven.
2. Description of the Prior Art
This invention comprises an improvement over the methods and apparatus disclosed in issued U.S. Pat. Nos. 3,767,496 issued Oct. 23, 1974, 3,802,942 issued Apr. 9, 1974 and 3,959,065 issued May 25, 1976, all of which are commonly owned by the same assignee as the present application. In each of these disclosures a tubular sleeve is formed which is telecopically assembled onto the article from below by a push-up mechanism. All of these disclosures pertain to the thermal constriction of a thin tubular sleeve of thermoplastic material which is telescoped upwardly over the upright container during their coincidental alignment and retention of the sleeve in place for selective and controlled heating using infrared radiation for the thermoconstrictive process. U.S. Pat. No. 4,246,059, also owned by the common assignee of this application, discloses a method and apparatus for forming a tubular sleeve of shrinkable polymer material from a predecorated web for making tubular neck labels. The tubular sleeves are formed on apparatus which constituted an earlier form of sleeve making equipment. The present apparatus comprises a distinct improvement over such earlier equipment for making the sleeve with much faster start-up time and more uniform heat sealing of the heat-fusion type joint where the label material is overlapped on a forming mandrel. Previously the prior art required making the labels for containers from preprinted or predecorated rolls of prepared material which were cut to length into individual blanks for forming the presized sleeves. The cut blanks were precisely placed on a cylindrical forming mandrel and heat sealed into tubular form on the mandrel, using individual heated sealing bars which varied in temperature and sealing capability. The sleeves were then applied directly to the containers or flat folded into stored condition in a multipack for subsequent application to the containers. However, their fusion seams varied in strength and uniformity throughout their length due to sealing bar variations.